INTERNATIONAL SPACE STATION: 1/ 236
SKYLAB: 1/ 9
SPACE SHUTTLE: 135 missions/355 crew and passengers
SALYUT: 6 space stations/ 48 visitors
U.S.S.R.
U.S.S.R./ Russia
U.S.
U.S.
China
TIANGONG: 2 / 7
April
2019
2010
2000
1990
1980
Duration of program
Origin
1971
MIR:1/104
Amalthea
3
Daphnis
Pan
Atlas
2
Prometheus
2
Pandora
2
Epimetheus
2
Janus
2
Methone
Pallene
Europa
5
Callisto
4
Io
5
Thalassa
Naiad
Perdita
Thebe
Metis
Adrastea
Phoebe
2
Dione
3
Rhea
3
Tethys
3
Enceladus
3
Mimas
3
Rosalind
Belinda
Desdemona
Cordelia
Ophelia
Bianca
Triton
Nereid
Proteus
Larissa
Despina
Galatea
Telesto
2
Calypso
2
Helene
3
Miranda
Oberon
Ariel
Umbriel
Titania
Puck
Portia
Juliet
Cressida
Charon
Styx
Nix
Kerberos
Hydra
Phobos
6
Deimos
Ganymede
5
Titan
4
Hyperion
3
Iapetus
3
Jupiter
8
Saturn
4
Venus
19
Mars
30
Mars
30
Mercury
2
Sun
10Missions
Asteroids
11
Moon
25
Moon
25
Neptune
1
Uranus
1
Pluto
1
Ultima
Thule
1
Halley’s
comet
5
Comets
11
Earth
INNER SOLAR SYSTEM
OUTER SOLAR SYTEM
ASTEROID BELT
Mission Origin
U.S .
U.S.S.R./Russia
Europe
U.S./Europe
Japan
China
Germany
India
Israel
LIFE ON MARS?
A procession of robotic craft have
explored Mars from all angles,
discovering a world that was once
much wetter and warmer—and
might even have supported life.
SATURN SOJOURN
Few missions have visited
the planet, but Cassini
arrived in 2004 and
explored for 13 years; data
are still being processed.
HALLEY’S COMET
On an eccentric orbit that
travels past Neptune, Halley
returns to the inner solar system
every 76 years. Various craft
studied its last visit, in 1986.
TURBULENT JUPITER
The first missions to the planet
revealed a ball of violent,
swirling gases. Some of Jupiter’s
moons have been studied for
the potential to harbor life.
THE MOON AND ITS PROSPECTS
Space companies are determining
whether there’s money to be made
on Earth’s nearest neighbor through
projects like mining, commercial
travel, and colonization.
ASTEROID ENCOUNTERS
Filled with protoplanetary bodies,
the asteroid belt holds clues to how
our solar system and planets formed.
Probes have visited and collected
samples from asteroids.
KUIPER BELT
Reaching the most distant bodies
in our solar system, the New
Horizons spacecraft was the first
to visit Pluto; it then flew on to
explore Ultima Thule.
Each colored line
represents a mission
since 1973 that stud-
ied a celestial body.
Lines are arranged in
chronological order
from the object out-
ward. Dotted lines
are failed missions.
LIVING AND WORKING WHILE ORBITING EARTH
International crews have continued to conduct research on Earth-orbiting stations, while
for 30 years NASA’s reusable space shuttles carried crew and cargo on a variety of missions.
NGM ART. MATTHEW TWOMBLY; ALEXANDER STEGMAIER. SOURCES: NASA; ASIF SIDDIQI, FORDHAM UNIVERSITY;
JONATHAN MCDOWELL, HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS; USGS ASTROGEOLOGY SCIENCE CENTER
Nearly half a century has elapsed since humans last visited the moon in 1972.
But we never stopped exploring. We’ve inhabited research stations orbiting Earth
(right) and sent robotic craft (below) to venture even farther into space to take
selfies on Mars, plunge into Jupiter, and investigate our solar system up close.
AFTER APOLLO
OBJECT SIZES AND ORBITAL DISTANCES ARE NOT TO SCALE.
n the 1960s our moon was
still very much a mystery.
To learn the most from
the Apollo visits, NASA selected
landing sites in a variety of lunar
terrains, including the dark, flat
plains sculpted by vanished lava
oceans and highlands formed by
meteor impacts.
From 1969 to 1972, U.S. astro-
nauts landed at six sites, each
chosen for different scientific
objectives. All of them were on the
moon’s mottled near side, where
the terrain had been studied
extensively by lunar orbiters and
Mission Control could remain in
direct contact with the astronauts.
Space agencies have sent probes,
with no people on them and thus
no need to worry about human
safety, to visit far-flung places in
the solar system. Spacecraft have
explored 60 other moons and even
set down on one, Saturn’s Titan.
On our own moon, robotic rovers
have left tracks at four sites.
China made history earlier
this year by setting its Chang’e 4
lander on the moon’s far side.
The first private lander to reach
the moon crashed in April, but the
Israeli nonprofit behind it quickly
announced plans to try again.
Not to be outdone, the U.S.
intends to send a series of landers
with technology to lay the ground-
work for astronauts to return.
I